.223 to 300BLK conversion issues when chambering

[Eurodriver]

I converted a bunch of LC brass to 300BLK over the last week or so. I measured the neck thickness and it is within spec before I converted it.

I just loaded up 15 rounds and tried to chamber a few and while it seats perfectly fine, it is a pain in the ass to extract. The bolt won't release without a really firm jolt and it happens whether I use the bolt release or slingshot it.

I measured all of the critical dimensions and they are identical to my Fiocchi 300BLK that does not do it so the issue is something I am not seeing or the tolerance is so tight that my $150 Starrett calipers aren't picking it up.

I've measured neck width, OAL, case length, bullet width, case width (at random points along the case) and case head diameter. They are all within .002" of the factory Fiocchi ammo except the case neck diameter which is exactly 0.332" on both my reloads and the Fiocchi.

What would cause this? Headspace?

ETA: After playing with it more, once I seat the rounds one time they no longer are a problem. So something is happening to the round when I chamber it.

ETA: It's headspace. Screwed the FL die in further and they cycle fine now.

[Onyx Z]

Yep, it sounds like a headspace issue. I see you figured it out on your own, good job!

[eddies66]

The 220 grain subsonic I buy from FOG ammo does the exact same thing but they shoot fine. Never had a malfunction after about 600 rounds.

[lysander]

tight chamber?

[Eurodriver]

Yep, it sounds like a headspace issue. I see you figured it out on your own, good job!

Thanks Onyx. All of the brass was just converted from 223 and I guess I was pretty weak handed on the resizing. I had to bump the shoulder back and it worked fine.

Eddie, I thought that it might still function but just wanted to double check. These were my first reloads for a semi auto rifle.

[williejc]

Just curious. What die brand are you using?

[GunnutAF]

Yep sizing die must kiss shell holder. Then you'll never have a chambering issue. No need to cam over just make sure it touches at full stroke.;) Had the same issues when I first got into the 300 Blk. Turned the sizing die down to touch holder -problem solved.

[themonk]

These are pricy but they make life a lot easier - http://www.sheridanengineering.com/index-2.htm

They sell slotted and non-slotted guages, get the slotted as it gives you more info when diagnosing any issues with new loads and different bullets.

[D.O.A.F.S.]

These are pricy but they make life a lot easier - http://www.sheridanengineering.com/index-2.htm

They sell slotted and non-slotted guages, get the slotted as it gives you more info when diagnosing any issues with new loads and different bullets.

+1 and as suggested get the slotted one.

[bigedp51]

Get the Hornady cartridge case headspace gauge and you will never need to buy another case gauge.

On top of this the Hornady gauge can be adjusted to read actual headspace.

Below a Colt Field gauge for the 5.56, 1.4736

http://i122.photobucket.com/albums/o254/bigedp51/headspacegauge006_zps3cdabdf4.jpg

Below the Colt headspace gauge in my calibrated Hornady cartridge case headspace gauge.

http://i122.photobucket.com/albums/o254/bigedp51/headspacegauge_zps14d3b71f.jpg

Below a fired unresized case in the Hornady gauge. And if you do not know how long your fired case is, how will you know how far to bump the shoulder?

http://i122.photobucket.com/albums/o254/bigedp51/headspacegauge005_zps20685e73.jpg

Below the same case after full length resizing and .003 shoulder bump.

http://i122.photobucket.com/albums/o254/bigedp51/headspacegauge004_zps4465b7bc.jpg

I now use my Wilson type case gauges as paper weights and pen holders.

http://i122.photobucket.com/albums/o254/bigedp51/penholder_zps4213e7d3.jpg

Eurodriver

We live in a plus and minus manufacturing world and no two resizing dies are the same and you need good case measurements to properly setup your dies and "NOT" over resize your cases and shorten their useful life.

Below is a very good "exaggerated" drawing of what happens when full length resizing a cartridge case. When full length resizing you need to know "where" your red dotted line is after the case is fired. After you know your fired length on a semiauto you bump the shoulder back .003 to .006 thousandths.

http://i122.photobucket.com/albums/o254/bigedp51/shouldersetback_zps59bf1b04.jpg

Your cases are binding because they are longer than the red dotted line and in the blue dotted line zone. Meaning your cases are too long and your die needs to be lowered. After these cases are fire formed you will need to remeasure these cases and possibly readjust your dies again.